How much of a drop in the pitman arm is anyone using with a 4" Alcan SUA lift, mine is flat, at least for now, just did the spring lift this weekend?

I have never had 4" springs so I can't tell you what to use. I used to have a LCAH SR with stock springs and I used a 2" drop pitman arm from a Jeep YJ. The XJ is about 3" and the ZJ is about 4". These pitman arms are about 5.75" long so they may be too short for your application.